OBJECTIVE: In the present study, cardiac autonomic functions in CSA patients were evaluated before and after percutaneous coronary intervention (PCI) using heart rate variability (HRV). METHODS: Thirty patients with CSA were recruited from cardiology outpatient clinics of VMMC and Safdarjung hospital, New Delhi, India. For each patient HRV parameters (LF, HF, LF:HF ratio, SDNN, RMSSD, total power, and pNN50) were gathered before and after PCI. Data were compiled and analyzed using licensed statistical software: SPSS version 21.0. RESULTS: Out of 30 subjects, SDNN (61.47+/-22.27 vs. 32.24+/-16.50ms, p<0.0001), RMSSD (53.86+/-31.41 vs. 28.81+/-23.80ms, p=0.001) and pNN50 (46.24+/-34.36 vs. 5.20+/-6.63, p<0.0001) in post-PCI were significantly higher as compared to the pre-PCI values. There were significant increases in both LF (1193ms(2)+/-302.04ms(2)vs. 1054.60ms(2)+/-208 ms(2), p<0.001) and HF (991.57+/-872.40ms(2)vs. 466.72ms(2)+/-257.93ms(2), p<0.0001), also in total power (3548.37ms(2)+/-807.73ms(2)vs. 2428 ms(2)+/-867.07 ms(2), p<0.0001) in post-PCI as compared to pre-PCI. The LF:HF ratio in pre-PCI was higher as compared to post-PCI (1.467+/-1.639 vs. 1.143+/-0.852, p=0.805), but the difference was not statistically significant. CONCLUSION: In this preliminary study, it is concluded that there is significant improvement in resting cardiovascular parameters, resting autonomic tone as measured by HRV which shows increase in both parasympathetic as well as sympathetic reactivity following revascularization by PCI in CSA patients. Hence, we also suggest that the use of noninvasive tests such as HRV should be done to stratify further risk of disease progression.